The present invention relates to a process for controlled radical polymerization in aqueous dispersion in the presence of selected nitroxyl radicals having a defined partition equilibrium between water and monomer as measured by their log p, wherein p is the partition coefficient of the nitroxyl radical in octanol and water.
Polymerization processes using water as a continuous dispersing phase wherein initially the monomers and after polymerization the polymers are dispersed are widely used for manufacturing polymers (aqueous dispersion polymerization). Mostly, water and a water-insoluble monomer, an emulgator and/or a protective colloid and a suitable initiator system are mixed by generally known methods building a monomer swollen micellar system or stabilized monomer droplets.
Of particular interest are emulsion polymerizations, wherein usually water soluble initiator systems are used.
The monomers are essentially insoluble in the aqueous phase and form finely distributed droplets therein. The addition of dispersing agents such as for example sodium dodecyl-sulfate is in many cases necessary to achieve such stable droplets and micelles. Examples of dispersing agents are for example given in xe2x80x9cUllmann Enzyklopxc3xa4die der technischen Chemie, Bd.10, 4. Auflage, Verlag Chemie, Weinheim (1975), page 449xe2x80x9d.
Several variations are known in the state of the art, for example emulgator free emulsion polymerization, mini emulsion polymerization and micro emulsion polymerization. These variations are characterized by changes of kind and amount of the emulgator and initiator systems leading to different polymer products especially with regard to molecular weight, polymer particle size and their distributions.
Polymers or copolymers prepared by free radical polymerization processes inherently have broad molecular weight distributions or polydispersities which are generally higher than about four. One reason for this is that most of the free radical initiators have half lives that are relatively long, ranging from several minutes to many hours, and thus the polymeric chains are not all initiated at the same time and the initiators provide growing chains of various lengths at any time during the polymerization process. Another reason is that the propagating chains in a free radical process can react with each other in processes known as combination and disproportionation, both of which are irreversibly chain-terminating reaction processes. In doing so, chains of varying lengths are terminated at different times during the reaction process, resulting in resins consisting of polymeric chains which vary widely in length from very small to very large and which thus have broad polydispersities. If a free radical polymerization process is to be used for producing narrow molecular weight distributions, then all polymer chains must be initiated at about the same time and termination of the growing polymer-chains by combination or disproportionation processes must be avoided.
A method to reduce polydispersity and to avoid the disadvantages of conventional radical polymerization has already been described by Solomon et al., U.S. Pat. No. 4,581,429, issued Apr. 8, 1986, wherein a free radical polymerization process is disclosed which controls the growth of polymer chains to produce short chain or oligomeric homopolymers and copolymers, including block and graft copolymers. The process employs an initiator having the formula (in part) Rxe2x80x2Rxe2x80x3Nxe2x80x94Oxe2x80x94X, where X is a free radical species capable of polymerizing unsaturated monomers. The reactions typically have low conversion rates. Specifically mentioned radical Rxe2x80x2Rxe2x80x3Nxe2x80x94O. groups are derived from 1,1,3,3 tetraethylisoindoline, 1,1,3,3 tetrapropylisoindoline, 2,2,6,6 tetramethylpiperidine, 2,2,5,5 tetramethylpyrrolidine or di-t-butylamine.
In WO 99/00426 emulsion polymerization of ethylenically unsaturated monomers in the presence of nitroxyl radicals has been described in greater detail, pointing out that the monomer droplets have a size of less or equal 500 nm.
Recently in EP 970973 emulsion polymerization in the presence of a stable free radical has been described, pointing out that the water solubility of the stable free radical is at least 0.1 g/l at 25xc2x0 C. Additionally, in WO 99/11674 the requirement of the molale solubility of the nitroxyl radicals in the aqueous medium is described as being at least 10xe2x88x926 mol/kg and most preferred at least 10xe2x88x921 mol/kg at 25xc2x0 C. and 1 bar.
In the instant invention it has been found, that the most important property of the nitroxyl radicals is not the good solubility in water but the partition equilibrium between water and monomer as reflected by the log p value of the nitroxyl. The right balance between solubility in water and solubility in the monomer droplets influences strongly the efficiency in terms of polydispersity, rate of polymerization and yield.
The partition coefficient log p (octanol/water) is a widely used parameter for example in rating the environmental impact of chemical compounds. Its calculation is described by W. M. Meylan, P. H. Howard in J. Pharmaceutical Sciences 84, (1995), 83-92.
One subject of the instant invention is a process for preparing an oligomer, a cooligomer, a polymer or a copolymer (block or random) by free radical polymerization in aqueous dispersion of at least one ethylenically unsaturated monomer or oligomer, which comprises forming an aqueous dispersion, having the monomer in the disperse phase and (co)polymerizing the monomer or monomers/oligomers at elevated temperature in the presence of
a) at least one stable free nitroxyl radical which has a log p (octanol/water) of between xe2x88x920.5 and 7.5 and which is selected from the group consisting of a compound of formula (A), (B), (C), (D), (E), (F), (G), (H) or (I) 
wherein
R is hydrogen, C1-C18alkyl which is uninterrupted or interrupted by one or more oxygen atoms, cyanoethyl, benzoyl, glycidyl, a monovalent radical of an aliphatic carboxylic-acid having 2 to 18 carbon atoms, of a cycloaliphatic carboxylic acid having 7 to 15 carbon atoms, or an xcex1,xcex2-unsaturated carboxylic acid having 3 to 5 carbon atoms or of an aromatic carboxylic acid having 7 to 15 carbon atoms;
R101 is C1-C12alkyl, C5-C7cycloalkyl, C7-C8aralkyl, C2-C18alkanoyl, C3-C5alkenoyl or benzoyl;
R102 is C1-C18alkyl, C5-C7cycloalkyl, C2-C8alkenyl unsubstituted or substituted by a cyano, carbonyl or carbamide group, or is glycidyl, a group of the formula xe2x80x94CH2CH(OH)xe2x80x94Z or of the formula xe2x80x94COxe2x80x94Z or xe2x80x94CONHxe2x80x94Z wherein Z is hydrogen, methyl or phenyl;
G6 is hydrogen and G5 is hydrogen or C1-C4alkyl, and
G1 and G3 are methyl and G2 and G4 are ethyl or propyl or G1 and G2 are methyl and G3 and G4 are ethyl or propyl;
R1, R2, R3 and R4 independently of each other are C1-C18alkyl, C3-C18alkenyl, C3-C18alkinyl, C1-C18alkyl, C3-C18alkenyl, C3-C18alkinyl which are substituted by OH, halogen or a group xe2x80x94Oxe2x80x94C(O)xe2x80x94R5, C2-C18alkyl which is interrupted by at least one O atom and/or NR5 group, C3-C12cycloalkyl or C6-C10aryl or R1 and R2 and/or R3 and R4 together with the linking carbon atom form a C3-C12cycloalkyl radical;
R5, R6 and R7 independently are hydrogen, C1-C18alkyl or C6-C10aryl;
R8 is hydrogen, OH, C1-C18alkyl, C3-C18alkenyl, C3-C18alkinyl;
C1-C18alkyl, C3-C18alkenyl, C3-C18alkinyl which are substituted by one or more OH, halogen or a group xe2x80x94Oxe2x80x94C(O)xe2x80x94R5, C2-C18alkyl which is interrupted by at least one O atom and/or NR5 group, C3-C12cycloalkyl or C6-C10aryl, C7-C9phenylalkyl, C5-C10heteroaryl, xe2x80x94C(O)xe2x80x94C1-C18alkyl, xe2x80x94Oxe2x80x94C1-C18alkyl or xe2x80x94COOC1-C18alkyl; and
R9, R10, R11 and R12 are independently hydrogen, phenyl or C1-C18alkyl; and
b) a free radical initiator.
The alkyl radicals in the various substituents may be linear or branched. Examples of alkyl containing 1 to 18 carbon atoms are methyl, ethyl, propyl, isopropyl, butyl, 2-butyl, isobutyl, t-butyl, pentyl, 2-pentyl, hexyl, heptyl, octyl, 2-ethylhexyl, t-octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, hexadecyl and octadecyl.
Alkenyl with 3 to 18 carbon atoms is a linear or branched radical as for example propenyl, 2-butenyl, 3-butenyl, isobutenyl, n-2,4pentadienyl, 3-methyl-2-butenyl, n-2-octenyl, n-2-dodecenyl, iso-dodecenyl, oleyl, n-2-octadecenyl oder n4-octadecenyl. Preferred is alkenyl with 3 bis 12, particularly preferred with 3 to 6 carbon atoms.
Alkinyl with 3 to 18 is a linear or branched radical as for example propinyl (xe2x80x94CH2xe2x80x94Cxe2x89xa1CH), 2-butinyl, 3butinyl, n-2-octinyl, oder n-2-octadecinyl. Preferred is alkinyl with 3 to 12, particularly preferred with 3 to 6 carbon atoms.
Examples for hydroxy substituted alkyl are hydroxy propyl, hydroxy butyl or hydroxy hexyl.
Examples for halogen substituted alkyl are dichloropropyl, monobromobutyl or trichlorohexyl.
C2-C18alkyl interrupted by at least one O atom is for example xe2x80x94CH2xe2x80x94CH2xe2x80x94Oxe2x80x94CH2xe2x80x94CH3, xe2x80x94CH2xe2x80x94CH2xe2x80x94Oxe2x80x94CH3xe2x80x94 or xe2x80x94CH2xe2x80x94CH2xe2x80x94Oxe2x80x94CH2xe2x80x94CH2xe2x80x94CH2xe2x80x94Oxe2x80x94CH2xe2x80x94CH3, xe2x80x94CH2xe2x80x94. It is preferably derived from polyethlene glycol. A general description is xe2x80x94((CH2)axe2x80x94O)bxe2x80x94H/CH3, wherein a is a number from 1 to 6 and b is a number from 2 to 10.
C2-C18alkyl interrupted by at least one NR5 group may be generally described as xe2x80x94((CH2)axe2x80x94NR5)bxe2x80x94H/CH3, wherein a, b and R5 are as defined above.
C3-C12cycloalkyl is typically, cyclopropyl, cyclopentyl, methylcyclopentyl, dimethylcyclopentyl, cyclohexyl, methylcyclohexyl or trimethylcyclohexyl.
C6-C10 aryl is for example phenyl or naphthyl, but also comprised are C1-C4alkyl substituted phenyl, C1-C4alkoxy substituted phenyl, hydroxy, halogen or nitro substituted phenyl. Examples for alkyl substituted phenyl are ethylbenzene, toluene, xylene and its isomers, mesitylene or isopropylbenzene. Halogen substituted phenyl is for example dichlorobenzene or bromotoluene.
Alkoxy substituents are typically methoxy, ethoxy, propoxy or butoxy and their corresponding isomers.
C7-C9phenylalkyl is benzyl, phenylethyl or phenylpropyl.
C5-C10heteroaryl is for example pyrrol, pyrazol, imidazol, 2,4,dimethylpyrrol, 1-methylpyrrol, thiophene, furane, furfural, indol, cumarone, oxazol, thiazol, isoxazol, isothiazol, triazol, pyridine, xcex1-picoline, pyridazine, pyrazine or pyrimidine.
If R is a monovalent radical of a carboxylic acid, it is, for example, an acetyl, propionyl, butyryl, valeroyl, caproyl, stearoyl, lauroyl, acryloyl, methacryloyl, benzoyl, cinnamoyl or xcex2-(3,5-di-tert-butylhydroxyphenyl)propionyl radical.
C1-C18alkanoyl is for example, formyl, propionyl, butyryl, octanoyl, dodecanoyl but preferably acetyl and C3-C5alkenoyl is in particular acryloyl.
The above compounds and their preparation are described in GB 2335190 and in GB 2342649.
Preferred is a process, wherein in formula A, B and C
R is hydrogen, C1-C18alkyl, cyanoethyl, benzoyl, glycidyl, a monovalent radical of an aliphatic, carboxylic acid;
R101, is C1-C12alkyl, C7-C8aralkyl, C2-C18alkanoyl, C3-C5alkenoyl or benzoyl;
R102 is C1-C18alkyl, glycidyl, a group of the formula xe2x80x94CH2CH(OH)-Z or of the formula xe2x80x94CO-Z, wherein Z is hydrogen, methyl or phenyl.
Another preferred process is, wherein in formula (D), (E), (F), (G), (H) and (I) at least two of R1, R2, R3 and R4 are ethyl, propyl or butyl and the remaining are methyl; or
R1 and R2 or R3 and R4 together with the linking carbon atom form a C5-C6cycloalkyl radical and one remaining substituents is ethyl, propyl or butyl.
Specific particularly suitable compounds are given in the following Table.
Preferably log p is from 0 to 5 and more preferably from 1 to 5.
Preferably the free radical initiator of component b) is a bis-azo compound, a peroxide or a hydroperoxide.
Specific preferred radical sources are 2,2xe2x80x2-azobisisobutyronitrile, 2,2xe2x80x2-azobis(2-methyl-butyronitrile), 2,2xe2x80x2-azobis(2,4-dimethylvaleronitrile), 2,2xe2x80x2-azobis(4-methoxy-2,4-dimethylvaleronitrile), 1,1xe2x80x2-azobis(1-cyclohexanecarbonitrile), 2,2xe2x80x2-azobis(isobutyramide) dihydrate, 2-phenylazo-2,4-dimethyl-4-methoxyvaleronitrile, dimethyl-2,2xe2x80x2-azobisisobutyrate, 2-(carbamoylazo)isobutyronitrile, 2,2xe2x80x2-azobis(2,4,4-trimethylpentane), 2,2xe2x80x2-azobis(2-methylpropane), 2,2xe2x80x2-azobis(N,Nxe2x80x2-dimethyleneisobutyramidine), free base or hydrochloride, 2,2xe2x80x2-azobis(2-amidinopropane), free base or hydrochloride, 2,2xe2x80x2-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)ethyl]propionamide} or 2,2xe2x80x2-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide; acetyl cyclohexane sulphonyl peroxide, diisopropyl peroxy dicarbonate, t-amyl pemeodecanoate, t-butyl pemeodecanoate, t-butyl perpivalate, t-amylperpivalate, bis(2,4-dichlorobenzoyl)peroxide, diisononanoyl peroxide, didecanoyl peroxide, dioctanoyl peroxide, dilauroyl peroxide, bis (2-methylbenzoyl) peroxide, disuccinic acid peroxide, diacetyl peroxide, dibenzoyl peroxide, t-butyl per 2-ethylhexanoate, bis-(4-chlorobenzoyl)-peroxide, t-butyl perisobutyrate, t-butyl permaleinate, 1,1-bis(t-butylperoxy)3,5,5-trimethylcyclohexane, 1,1-bis(t-butylperoxy)cyclohexane, t-butyl peroxy isopropyl carbonate, t-butyl perisononaoate, 2,5-dimethylhexane 2,5dibenzoate, t-butyl peracetate, t-amyl perbenzoate, t-butyl perbenzoate, 2,2-bis (t-butylperoxy) butane, 2,2 bis (t-butylperoxy) propane, dicumyl peroxide, 2,5dimethylhexane-2,5-di-t-butylperoxide, 3-t-butylperoxy 3-phenylphthalide, di-t-amyl peroxide, xcex1,xcex1xe2x80x2-bis(t-butylperoxy isopropyl) benzene, 3,5-bis (t-butylperoxy)3,5-dimethyl 1,2-dioxolane, di-t-butyl peroxide, 2,5-dimethylhexyne-2,5-di-t-butylperoxide, 3,3,6,6,9,9-hexamethyl 1,2,4,5-tetraoxa cyclononane, p-menthane hydroperoxide, pinane hydroperoxide, diisopropylbenzene mono-xcex1-hydroperoxide, cumene hydroperoxide or t-butyl hydroperoxide.
The radical initiator has preferably a water solubility of at least 1 g/l at 20xc2x0 C.
Most preferred are the following compounds, which are all commercially available.
It is also possible to use combinations of Fe-compounds or Co-compounds with peroxo salts or salts of bisulfites or hydrosulfites. These combinations are known as redox systems.
Preferably the ethylenically unsaturated monomer is selected from the group consisting of styrene, substituted styrene, conjugated dienes, acrolein, vinyl acetate, vinylpyrrolidone, vinylimidazole, maleic anhydride, (alkyl)acrylic acidanhydrides, (alkyl)acrylic esters, (meth)acrylonitriles, (alkyl)acrylamides.
More preferred the ethylenically unsaturated monomer is an acrylic acid ester, acrylamide, acryinitrile, methacrylic acid ester, methacrylamide, methacrylnitrile.
A preferred ethylenically unsaturated monomer conforms to formula CH2xe2x95x90C(Ra)xe2x80x94(Cxe2x95x90Z)xe2x80x94Rb, wherein Ra is hydrogen or C1-C4alkyl, Rb is NH2, glycidyl, unsubstituted C1-C18alkoxy, C2-C100alkoxy interrupted by at least one N and/or O atom, or hydroxy-substituted C1-C18alkoxy, unsubstituted C1-C18alkylamino, di(C1-C18alkyl)amino, hydroxy-substituted C1-C18alkylamino or hydroxy-substituted di(C1-C18alkyl)amino or xe2x80x94Oxe2x80x94CH2xe2x80x94CH2xe2x80x94N(CH3)2;
Z is oxygen or sulfur.
Examples for Rb as C2-C100alkoxy interrupted by at least one O atom are of formula 
wherein Rc is C1-C25alkyl, phenyl or phenyl substituted by C1-C18alkyl, Rd is hydrogen or methyl and v is a number from 1 to 50. These monomers are for example derived from non ionic surfactants by acrylation of the corresponding alkoxylated alcohols or phenols. The repeating units may be derived from ethylene oxide, propylene oxide or mixtures of both.
Further examples of suitable acrylate or methacrylate monomers are given below.
Further acrylate monomers are 
Examples for suitable monomers other than acrylates are 
Preferably Ra is hydrogen or methyl, Rb is NH2, gycidyl, unsubstituted or with hydroxy substituted C1-C4alkoxy, unsubstituted C1-C4alkylamino, di(C1-C4alkyl)amino, hydroxy-substituted C1-C4alkylamino or hydroxy-substituted di(C1-C4alkyl)amino; and
Z is oxygen.
Preferably the aqueous phase is from 25 to 95% more preferably from 40 to 80% and most preferred from 45 to 75% by weight, based on the total mixture.
The total mixture contains water, at least one monomer, the above mentioned regulator and initiator and in many cases at least one surfactant and/or a organic solvent.
Optionally other water miscible solvents may be present usually less than 10% by weight based on the water content. Exemplary cosolvents useful in the present invention may be selected from the group consisting of aliphatic alcohols, glycols, ethers, glycol ethers, pyrrolidines, N-alkyl pyrrolidinones, N-alkyl pyrrolidones, polyethylene glycols, polypropylene glycols, amides, carboxylic acids and salts thereof, esters, organosulfides, sulfoxides, sulfones, alcohol derivatives, hydroxyether derivatives such as butyl carbitol or cellosolve, amino alcohols, ketones, and the like, as well as derivatives thereof and mixtures thereof. Specific examples include methanol, ethanol, propanol, dioxane, ethylene glycol, propylene glycol, diethylene glycol, glycerol, dipropylene glycol, tetrahydrofuran, and other water-soluble or water-miscible materials, and mixtures thereof.
Preferred are water, water alcohol mixtures, water ethylene glycol or propylene glycol mixtures, water acetone, water tetrahydrofurane, or water dimethylformamide mixtures.
Preferably the solids content of the resulting polymer dispersion is between 15-60% by weight.
Preferably the nitroxyl radical of component a) is present in an amount of from 0.001 mol-% to 20 mol-%, based on the monomer or monomer mixture.
In case of monomer mixtures an average molecular weight is calculated.
Preferably the free radical initiator is present in an amount of from 0.01 mol-% to 20 mol-%, more preferably from 0.1 mol-% to 10 mol-% and most preferably from 0.2 mol-% to 5 mol-%, based on the monomer or monomer mixture.
Preferably the molar ratio of free radical initiator to stable free nitroxyl radical is from 20:1 to 1:2, more preferably from 10:1 to 1:2.
The temperature for polymerization is preferably from 60xc2x0 C. to 180xc2x0 C., more preferably from 80xc2x0 C. to 140xc2x0 C. and most preferably from 80xc2x0 C. to 110xc2x0 C.
The pressure during the reaction depends on the temperature applied and is preferably between 0.1 bar and 20 bar, more preferably between 1 and 10 bar.
The reaction mixture may also contain a buffer to adjust and maintain the pH value, preferably between 4.5 and 9. Phosphate or citric acid buffers are preferred.
The process is particularly useful for the preparation of block copolymers.
Block copolymers are, for example, block copolymers of polystyrene and polyacrylate (e.g., poly(styrene-co-acrylate) or poly(styrene-co-acrylate-co-styrene). They are usefull as adhesives or as compatibilizers for polymer blends or as polymer toughening agents. Poly(methylmethacrylate-co-acrylate) diblock copolymers or poly(methylacrylate-co-acrylate-co-methacrylate) triblock copolymers) are useful as dispersing agents for coating systeme, as coating additives (e.g. theological agents, compatibilizers, reactive diluents) or as resin component in coatings (e.g. high solid paints) Block copolymers of styrene, (meth)acrylates and/or acrylonitrile are useful for plastics, elastomers and adhesives.
Furthermore, block copolymers of this invention, wherein the blocks alternate between polar monomers and non-polar monomers, are useful in many applications as amphiphilic surfactants or dispersants for preparing highly uniform polymer blends.
Particularly, emulsion polymerization is especially suitable to build-up polymer particles with specific morphology. For example, core/shell structures can be achieved by consecutively changing monomers during polymerization. These special particles are useful for improving impact resistance of plastics. Oftenly, these core/shell structures are polymer blends of at least two types of polymers which are formed within the polymer particle during emulsion polymerization. By applying controlled free radical polymerization during consecutive monomer feed, block copolymers are formed which improve the compatibilizing effect of the different polymers within the polymer particle. Furthermore, core/shell structures can be synthesized by grafting a different monomer during emulsion polymerization on polymer particles containing unsaturations, e.g. butadiene (co-)polymers. Applying controlled free radical polymerization within this grafting process, graft polymers with uniform graft arm lengths and even new graft polymers are accessible.
Consequently the formation of block and graft polymers is a subject of the present invention.
The (co)polymers of the present invention may have a number average molecular weight from 1 000 to 400 000 g/mol, preferably from 2 000 to 250 000 g/mol and, more preferably, from 2 000 to 200 000 g/mol. The number average molecular weight may be determined by size exclusion chromatography (SEC), matrix assisted laser desorption/ionization mass spectrometry (MALDI-MS) or, if the initiator carries a group which can be easily distinguished from the monomer(s), by NMR spectroscopy or other conventional methods.
The polymers or copolymers of the present invention have preferably a polydispersity of from 1.1 to 2, more preferably of from 1.2 to 1.8.
The average particle diameter of the dispersed polymer particles is preferably from 25 nm to 1000 nm, more preferably 200 nm to 700 nm. Particle size may for example be measured by a high speed centrifuge or by photon correlation spectroscopy.
The particle size distribution may be monomodal or bimodal.
The process of emulsion polymerization per se is known and for example described in WO 99/00426 or in WO00/50480. It may be carried out as a batch process or in a continuous or semi continuous process.
The initiator and/or regulator may for example be added at the beginning of the reaction, however it is also possible to add one or the other in portions or continuously at the beginning and during the reaction.
Suitable surfactants or surface active compounds which may be added are known in the art. The amounts typically used range from 0.01% by weight to 10% by weight, based on the monomer or monomers.
Suitable surface active compounds are protective colloids such as polyvinylalcohols, starch, cellulose derivatives or copolymers containing vinylpyrrolidone. Further examples are given in xe2x80x9cHouben-Weyl, Methoden der Organischen Chemie, Band XIV/1, Makromolekulare Stoffe, G. Thieme Verlag Stuttgart 1961, 411-420xe2x80x9d.
Typical surfactants useful in the present invention are of nonionic, cationic or anionic type.
Examples for anionic surfactants are alkali and ammonium salts of C12-C18alkylsulfonic acid, dialkyl esters of succinic acid or sulfuric acid halfesters of ethoxylated alkanoles. These compounds are known for example from U.S. Pat. No. 4,269,749 and largely items of commerce, such as under the trade name Dowfax(copyright) 2A1 (Dow Chemical Company).
Nonionic surfactants are for example aliphatic or araliphatic compounds such as ethoxylated phenols (mon, di, tri) with an ethoxylation degree of 3 to 50 and alkyl groups in the range from C4-C9, ethoxylated long chain alcohols or polyethyleneoxide/polypropyleneoxide block copolymers.
The emulsion polymerization may be carried out as seed free process or according to a seed-latex process which seed latex may also be prepared in situ. Such processes are known and for example described in EP-A-614 922 or in EP-A-567 812.
The present invention also encompasses in the synthesis novel block, multi-block, star, gradient, random, hyperbranched and dendritic copolymers, as well as graft copolymers.
The polymers prepared by the present invention are useful for following applications:
adhesives, detergents, dispersants, emulsifiers, surfactants, defoamers, adhesion promoters, corrosion inhibitors, viscosity improvers, lubricants, rheology modifiers, thickeners, crosslinkers, paper treatment, water treatment, electronic materials, paints, coatings, photography, ink materials, imaging materials, superabsorbants, cosmetics, hair products, preservatives, biocide materials or modifiers for asphalt, leather, textiles, ceramics and wood.
Because the present polymerizaton is a xe2x80x9clivingxe2x80x9d polymerization, it can be started and stopped practically at will. Furthermore, the polymer product retains the functional alkoxyamine group allowing a continuation of the polymerization in a living matter. Thus, in one embodiment of this invention, once the first monomer is consumed in the initial polymerizing step a second monomer can then be added to form a second block on the growing polymer chain in a second polymerization step. Therefore it is possible to carry out additional polymerizations with the same or different monomer(s) to prepare multi-block copolymers.
Furthermore, since this is a radical polymerization, blocks can be prepared in essentially any order. One is not necessarily restricted to preparing block copolymers where the sequential polymerizing steps must flow from the least stabilized polymer intermediate to the most stabilized polymer intermediate, such as is the case in ionic polymerization. Thus it is possible to prepare a multi-block copolymer in which a polyacrylonitrile or a poly(meth)-acrylate block is prepared first, then a styrene or butadiene block is attached thereto, and so on.